Datasheet
1997 Microchip Technology Inc. DS30272A-page 49
PIC16C71X
8.2 Oscillator Configurations
8.2.1 OSCILLATOR TYPES
The PIC16CXX can be operated in four different oscil-
lator modes. The user can program two configuration
bits (FOSC1 and FOSC0) to select one of these four
modes:
• LP Low Power Crystal
• XT Crystal/Resonator
• HS High Speed Crystal/Resonator
• RC Resistor/Capacitor
8.2.2 CRYSTAL OSCILLATOR/CERAMIC
RESONATORS
In XT, LP or HS modes a crystal or ceramic resonator
is connected to the OSC1/CLKIN and OSC2/CLKOUT
pins to establish oscillation (Figure 8-4). The
PIC16CXX Oscillator design requires the use of a par-
allel cut crystal. Use of a series cut crystal may give a
frequency out of the crystal manufacturers specifica-
tions. When in XT, LP or HS modes, the device can
have an external clock source to drive the OSC1/
CLKIN pin (Figure 8-5).
FIGURE 8-4: CRYSTAL/CERAMIC
RESONATOR OPERATION
(HS, XT OR LP
OSC CONFIGURATION)
FIGURE 8-5: EXTERNAL CLOCK INPUT
OPERATION (HS, XT OR LP
OSC CONFIGURATION)
C1
C2
XTAL
OSC2
Note1
OSC1
RF
SLEEP
PIC16CXXX
RS
See Table 8-1 and Table 8-1 for recommended values of
C1 and C2.
Note 1: A series resistor may be required for AT strip
cut crystals.
2: The buffer is on the OSC2 pin.
(2)
To internal
logic
OSC1
OSC2
Open
Clock from
ext. system
PIC16CXXX
TABLE 8-1: CERAMIC RESONATORS,
PIC16C71
TABLE 8-2: CAPACITOR SELECTION
FOR CRYSTAL OSCILLATOR,
PIC16C71
Ranges Tested:
Mode Freq OSC1 OSC2
XT 455 kHz
2.0 MHz
4.0 MHz
47 - 100 pF
15 - 68 pF
15 - 68 pF
47 - 100 pF
15 - 68 pF
15 - 68 pF
HS 8.0 MHz
16.0 MHz
15 - 68 pF
10 - 47 pF
15 - 68 pF
10 - 47 pF
These values are for design guidance only. See
notes at bottom of page.
Resonators Used:
455 kHz Panasonic EFO-A455K04B ± 0.3%
2.0 MHz Murata Erie CSA2.00MG ± 0.5%
4.0 MHz Murata Erie CSA4.00MG ± 0.5%
8.0 MHz Murata Erie CSA8.00MT ± 0.5%
16.0 MHz Murata Erie CSA16.00MX ± 0.5%
All resonators used did not have built-in capacitors.
Mode Freq OSC1 OSC2
LP 32 kHz
200 kHz
33 - 68 pF
15 - 47 pF
33 - 68 pF
15 - 47 pF
XT 100 kHz
500 kHz
1 MHz
2 MHz
4 MHz
47 - 100 pF
20 - 68 pF
15 - 68 pF
15 - 47 pF
15 - 33 pF
47 - 100 pF
20 - 68 pF
15 - 68 pF
15 - 47 pF
15 - 33 pF
HS 8 MHz
20 MHz
15 - 47 pF
15 - 47 pF
15 - 47 pF
15 - 47 pF
These values are for design guidance only. See
notes at bottom of page.